Confocal microscopy images of (A) ROS, SA, NO, and (B) mitochondrial membrane potential changes in MCF-7 cells and 4T1 cells after the treatment of TFENs for 4 h (scare bar: 50 μm). (C) Western blot analysis of cleaved caspase-3 and BCL-2 in MCF-7 cells and 4T1 cells receiving the treatment of TFENs for 24 and 48 h, respectively. Cell population profiles of (D) MCF-7 and (E) 4T1 cells in various cell cycle phases after co-incubation for 12 and 24 h, respectively. Each point represents the mean ± SEM (n = 3). ∗P < 0.05, ∗∗P < 0.01. ns, no significance). (F) Western blot analysis of cyclin A and cyclin B in MCF-7 cells and 4T1 cells receiving the treatment of TFENs for 24 and 48 h, respectively. (G) Schematic illustration of the pro-apoptotic mechanism of TFENs against cancer cells.